The present invention relates to a wireless device, a control method for a wireless communication system, and a wireless communication system.
A recent advance in the information communication technology has resulted in the development of many electrical appliances with the network communication function. Those electrical appliances, used in the home or offices, have computerized houses and buildings, leading to the development of a technology for providing more convenient, comfortable living environments.
On the other hand, connecting those electrical appliances to a network requires network construction work in the home and buildings, and the network construction work requires technical knowledge about the communication cable wiring and connections as well as hard work and high construction costs. Therefore, there is a need for building a network without doing network construction work.
To satisfy this need, a wireless network technology has been developed. This network technology uses the wireless communication method and allows wireless devices, which cannot directly communicate each other, to communicate via intermediary relay devices (wireless devices that relays communication), thus enabling a plurality of wireless devices to communicate each other with no need to do the network construction work. Such a wireless network, generally called an ad hoc network, is a network where data communication among wireless devices, including base stations, fixed stations, and mobile stations, is performed via a plurality of intermediary wireless devices. The following technologies are disclosed as a technology for building a network where data is relayed via wireless devices (For example, see JP-A-11-239176, JP-A-2003-115858).
In an ad hoc network, the selection of a communication route composed of wireless devices, along which data is passed during the communication, largely affects the throughput and the reliability of the whole network system and the ease of system management. Therefore, the technology for selecting and determining the best communication route is important.
The most popular conventional method for selecting and determining the best communication route from a plurality of communication routes is to select a communication route with the minimum number of hops (the number of intermediary relay devices).
However, when an intermediary relay device moves from one place to another or the power is turned off after a communication route is determined, the communication route using the intermediary relay device cannot be used. As a result, the source wireless device using this intermediary relay device as one of intermediary relay devices of the communication route must search for another communication route to the destination wireless device again.
In general, this communication route search is complex and time-consuming. Another problem is that, immediately after an intermediary relay device moves or the power is turned off, a data packet being transferred is stored in the buffer of the intermediary relay device until a new destination is found. When the buffer of the intermediary relay device becomes full, a packet loss may occur.
Searching for a new communication route also requires the transmission of many data packets and, therefore, more packets tend to be lost due to an increase in the traffic. A packet loss also involves the frequent retransmission of a packet at an application level, meaning that more and more wasteful data packets are generated.
Therefore, in such a network, it is important to select a route that does not require a repeated search for a route.